Alignment of a specimen for inspection and other processes

Abstract

Methods and systems for setting up alignment of a specimen are provided. One system includes computer subsystem(s) configured for acquiring two-dimensional (2D) images generated from output of a detector of an output acquisition subsystem at template locations in corresponding areas of printed instances on a specimen. The computer subsystem(s) determine offsets in x and y directions between the template locations using the 2D images and determine an angle of the specimen with respect to the output acquisition subsystem based on the offsets. If the angle is greater than a predetermined value, the computer subsystem(s) rotate the specimen and repeat the steps described above. If the angle is less than the predetermined value, the computer subsystem(s) store one of the 2D images for alignment of the specimen in a process performed on a specimen. The 2D images may include multi-mode images, which may be fused prior to determining the offsets.

What is claimed is: 
     
       1. A system configured for setting up alignment of a specimen, comprising:
 an output acquisition subsystem comprising at least an energy source and a detector, wherein the energy source is configured to generate energy that is directed to the specimen, wherein the detector is configured to detect energy from the specimen and to generate output responsive to the detected energy, and wherein the output acquisition subsystem is configured to direct the energy to the specimen and to detect the energy from the specimen with first and second modes; and 
 one or more computer subsystems configured for:
 acquiring two-dimensional images generated from the output of the detector at template locations in corresponding areas of printed instances on the specimen, wherein the two-dimensional images comprise a first image acquired at a first of the template locations and at least one additional image acquired at one or more other of the template locations, and wherein said acquiring comprises acquiring first and second mode two-dimensional images generated with the first and second modes, respectively, at the template locations in the corresponding areas of the printed instances on the specimen, generating the first image from the first and second mode two-dimensional images acquired at the first of the template locations, and generating the at least one additional image from the first and second mode two-dimensional images generated at the one or more other of the template locations; 
 determining offsets in x and y directions between the template locations, wherein determining the offsets comprises aligning the first image to the at least one additional image; 
 determining an angle of the specimen with respect to the output acquisition subsystem based on the offsets in the x and y directions; 
 comparing the determined angle to a predetermined value; 
 when the determined angle is greater than the predetermined value, rotating the specimen and repeating the acquiring, determining the offsets, determining the angle, and comparing steps; and 
 when the determined angle is less than the predetermined value, storing the first image for use in alignment of the specimen to the output acquisition subsystem during a process performed on the specimen. 
 
 
     
     
       2. The system of  claim 1 , wherein the detector comprises a photomultiplier tube. 
     
     
       3. The system of  claim 1 , wherein the output of the detector comprises non-imaging output. 
     
     
       4. The system of  claim 1 , wherein the one or more computer subsystems are further configured for acquiring additional two-dimensional images generated with the second mode at the template locations in the corresponding areas of the printed instances on the specimen, wherein the additional two-dimensional images comprise a second image acquired at the first of the template locations with the second mode and at least one other image acquired at the one or more other of the template locations with the second mode, and wherein determining the offsets further comprises determining a first of the offsets in the x and y directions by aligning the first image to the at least one additional image and determining a second of the offsets in the x and y directions by aligning the second image to the at least one other image. 
     
     
       5. The system of  claim 4 , wherein the first image and the at least one additional image comprise only horizontal patterns, and wherein the second image and the at least one other image comprise only vertical patterns. 
     
     
       6. The system of  claim 1 , wherein generating the first image and generating the at least one additional image comprises image fusion. 
     
     
       7. The system of  claim 1 , wherein the first mode two-dimensional images comprise only horizontal patterns, and wherein the second mode two-dimensional images comprise only vertical patterns. 
     
     
       8. The system of  claim 1 , wherein the offsets in the x and y directions are sub-pixel offsets in the x and y directions. 
     
     
       9. The system of  claim 1 , wherein said aligning does not comprise projecting patterned features in the first image and the at least one additional image in the x or y direction. 
     
     
       10. The system of  claim 1 , wherein a number of the at least one additional image acquired and used for determining the offsets is less than a number of the at least one additional image acquired in repeating the acquiring and used for repeating determining the offsets. 
     
     
       11. The system of  claim 1 , wherein the output acquisition subsystem and the one or more computer subsystems are further configured for performing the process on the specimen by acquiring at least one runtime two-dimensional image generated from the output of the detector at one or more of the template locations in the corresponding areas of the printed instances on the specimen, determining the offsets in the x and y directions between the stored first image and the one or more of the template locations by aligning the stored first image to the at least one runtime two-dimensional image, and performing the determining the angle, comparing, rotating, and repeating until the determined angle is less than the predetermined value. 
     
     
       12. The system of  claim 1 , further comprising a user interface configured for displaying information to and receiving input from a user, wherein the input comprises a two-dimensional size of the template locations. 
     
     
       13. The system of  claim 1 , further comprising a user interface configured for displaying information to and receiving input from a user, wherein the input comprises one or more of one or more parameters used for acquiring the two-dimensional images, a threshold used for said aligning, a quality threshold applied to the two-dimensional images, the predetermined value used for the comparing step, and one or more parameters used for the alignment of the specimen performed during the process. 
     
     
       14. The system of  claim 1 , wherein the process performed on the specimen comprises inspection, and wherein the inspection comprises detecting defects on the specimen based on output of the detector of the output acquisition subsystem generated during the inspection. 
     
     
       15. The system of  claim 1 , wherein the specimen comprises a wafer. 
     
     
       16. The system of  claim 1 , wherein the energy directed to the specimen comprises light, and wherein the energy detected from the specimen comprises light. 
     
     
       17. The system of  claim 1 , wherein the energy directed to the specimen comprises electrons, and wherein the energy detected from the specimen comprises electrons. 
     
     
       18. A non-transitory computer-readable medium, storing program instructions executable on a computer system for performing a computer-implemented method for setting up alignment of a specimen, wherein the computer-implemented method comprises:
 acquiring two-dimensional images generated from output of a detector of an output acquisition subsystem at template locations in corresponding areas of printed instances on the specimen, wherein the two-dimensional images comprise a first image acquired at a first of the template locations and at least one additional image acquired at one or more other of the template locations;
 wherein the output acquisition subsystem comprises at least an energy source and the detector, wherein the energy source is configured to generate energy that is directed to the specimen, wherein the detector is configured to detect energy from the specimen and to generate the output responsive to the detected energy, and wherein the output acquisition subsystem is configured to direct the energy to the specimen and to detect the energy from the specimen with first and second modes; and 
 wherein said acquiring comprises acquiring first and second mode two-dimensional images generated with the first and second modes, respectively, at the template locations in the corresponding areas of the printed instances on the specimen, generating the first image from the first and second mode two-dimensional images acquired at the first of the template locations, and generating the at least one additional image from the first and second mode two-dimensional images generated at the one or more other of the template locations; 
 
 determining offsets in x and y directions between the template locations, wherein determining the offsets comprises aligning the first image to the at least one additional image; 
 determining an angle of the specimen with respect to the output acquisition subsystem based on the offsets in the x and y directions; 
 comparing the determined angle to a predetermined value; 
 when the determined angle is greater than the predetermined value, rotating the specimen and repeating the acquiring, determining the offsets, determining the angle, and comparing steps; and 
 when the determined angle is less than the predetermined value, storing the first image for use in alignment of the specimen to the output acquisition subsystem during a process performed on the specimen, wherein the acquiring, determining the offsets, determining the angle, comparing, rotating, repeating, and storing steps are performed by the computer system. 
 
     
     
       19. A computer-implemented method for setting up alignment of a specimen, comprising:
 acquiring two-dimensional images generated from output of a detector of an output acquisition subsystem at template locations in corresponding areas of printed instances on the specimen, wherein the two-dimensional images comprise a first image acquired at a first of the template locations and at least one additional image acquired at one or more other of the template locations;
 wherein the output acquisition subsystem comprises at least an energy source and the detector, wherein the energy source is configured to generate energy that is directed to the specimen, wherein the detector is configured to detect energy from the specimen and to generate the output responsive to the detected energy, and wherein the output acquisition subsystem is configured to direct the energy to the specimen and to detect the energy from the specimen with first and second modes; and 
 wherein said acquiring comprises acquiring first and second mode two-dimensional images generated with the first and second modes, respectively, at the template locations in the corresponding areas of the printed instances on the specimen, generating the first image from the first and second mode two-dimensional images acquired at the first of the template locations, and generating the at least one additional image from the first and second mode two-dimensional images generated at the one or more other of the template locations; 
 
 determining offsets in x and y directions between the template locations, wherein determining the offsets comprises aligning the first image to the at least one additional image; 
 determining an angle of the specimen with respect to the output acquisition subsystem based on the offsets in the x and y directions; 
 comparing the determined angle to a predetermined value; 
 when the determined angle is greater than the predetermined value, rotating the specimen and repeating the acquiring, determining the offsets, determining the angle, and comparing steps; and 
 when the determined angle is less than the predetermined value, storing the first image for use in alignment of the specimen to the output acquisition subsystem during a process performed on the specimen, wherein the acquiring, determining the offsets, determining the angle, comparing, rotating, repeating, and storing steps are performed by one or more computer subsystems.